Astronomers have discovered 11 new streams of alien stars in the Milky Way, gobbled up from other smaller galaxies. A three-year survey of the night sky, using one of the most powerful digital cameras in the world, revealed the tendrils of stolen stars. 

Most of the 250 billion stars in the pinwheel-shaped Milky Way formed together. But our home galaxy has also acted as a cosmic cannibal, swallowing up other galaxies over billions of years.

The 11 new stellar streams eaten by the Milky Way were discovered during the first three years of operation of the Dark Energy Survey.

It follows the earlier identification of around two dozen likely streams of stellar intruders by earlier surveys.

University of Chicago graduate student Nora Shipp led the project to detect new streams of stars in our Galaxy. She said: “We’re interested in these streams because they teach us about the formation and structure of the Milky Way and its dark matter halo.

“Stellar streams give us a snapshot of a larger galaxy being built out of smaller ones. These discoveries are possible because DES is the widest, deepest and best-calibrated survey out there.”

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The survey uses a camera attached to a giant U.S. telescope at the Cerro Tolelo Inter-American Observatory in Chile. The camera is mounted on the National Science Foundation’s 4-meter Blanco telescope.

Its images are so huge and detailed that they have to be processed by a supercomputer at the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign.

The device, called the Dark Energy Camera, has taken around 40,000 photographs to image an eighth of the entire sky, producing terabytes of data. A terabyte is equal to more than 700 million floppy disks!

Its survey has given space scientists information about 400 million astronomical objects, from nearby stars to distant galaxies. The data has been released online to allow anyone to study it and potentially make discoveries.

The survey has also discovered numerous dwarf galaxies in the Milky Way’s neighbourhood. Despite being so close, they have been a challenge to find because they are so faint and diffuse.

The survey is helping astronomers try to understand invisible forces in the Universe called dark energy and dark matter.

Dr Knut Olsen, team leader National Optical Astronomy Observatory’s Data Lab, said: “The survey data extend deep and wide, to stars 40 million times fainter than the human eye can see, covering an eighth of the entire sky.”

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